BIO 1140 Lecture 7

What is Type 1 diabetes?

An autoimmune disease where the immune system destroys insulin-producing cells in the pancreas.

What happens when insulin is absent in Type 1 diabetes?

Blood glucose levels increase.

What is signal transduction?

The conversion of one type of signal into another inside a cell.

What are the three stages of cell signaling?

Signal reception, signal transduction, and cellular response.

What happens during signal reception?

A signaling molecule binds to a receptor.

What happens during signal transduction?

The signal is relayed and amplified inside the cell.

What happens during the cellular response?

The cell produces a specific effect or action.

What are intracellular signaling molecules?

Molecules that relay signals inside the cell during transduction.

What types of molecules can act as signals?

Proteins, peptides, amino acids, steroids, fatty acid derivatives, and gases.

Give an example of a protein signal.

Insulin (controls blood glucose).

Give an example of a peptide signal.

Oxytocin (involved in lactation and social bonding).

Give an example of an amino acid signal.

Glutamate (involved in learning and memory).

Give an example of a steroid signal.

Cortisol (involved in metabolism and stress response).

Give an example of a fatty acid derivative signal.

Prostaglandins (involved in inflammation, pain, and fever).

Give an example of a gas signal.

Nitric oxide (causes blood vessel dilation).

What are endocrine signals?

Hormones that act over long distances in the body.

What types of signals act locally?

Paracrine, synaptic, and contact-dependent signals.

What are paracrine signals?

Local signals like growth factors, inflammatory molecules, and gases.

What determines if a signal acts short or long range?

The type of signaling molecule and its mechanism of delivery.

Where do most signaling molecules bind?

Cell-surface receptors.

Why do most signaling molecules bind to surface receptors?

They are large and hydrophilic and cannot cross the membrane.

Which signaling molecules can cross the membrane?

Small, hydrophobic molecules.

Where do hydrophobic signaling molecules bind?

Intracellular receptors.

Give an example of a molecule that uses intracellular receptors.

Steroid hormones like cortisol.

How does nitric oxide (NO) act as a signal?

It diffuses into cells and binds directly to intracellular receptors.

What enzyme does NO activate?

Guanylyl cyclase.

What does guanylyl cyclase produce?

Cyclic GMP (cGMP).

What is the effect of cGMP in smooth muscle cells?

It causes relaxation of blood vessels.

What are the three main types of cell-surface receptors?

G-protein-coupled receptors, enzyme-coupled receptors, and ion-channel receptors.

What are ion-channel receptors?

Receptors that open or close channels in response to a signal.

What happens in a signal transduction pathway?

Each intracellular signaling molecule activates or generates another signaling molecule.

What is an effector protein?

A protein that directly changes the behavior of the target cell.

What happens when a cell-surface receptor binds a signal?

It creates a new intracellular signal.

What does the last molecule in a signaling pathway do?

It activates an effector protein.

What types of proteins can effector proteins be?

Enzymes, transcription factors, or cytoskeletal proteins.

What is a signal transduction pathway?

A series of molecular events that converts an external signal into a specific internal response.

What are the main roles of intracellular signaling molecules?

Relay, amplify, integrate, receive feedback, and distribute signals.

What types of molecules can intracellular signaling molecules be?

Proteins or small messengers like cAMP or cGMP.

What does signal relay mean?

Passing the signal from one molecule to another inside the cell.

How does relay occur in signaling proteins?

Through conformational changes that may activate the protein.

What is signal amplification?

Increasing the strength of a signal so many molecules are activated.

What type of enzyme is involved in amplification?

Kinase.

What does a kinase do?

Adds phosphate groups to proteins (phosphorylation).

What is feedback in signaling pathways?

Regulation of signaling proteins by positive or negative feedback.

Why is feedback important?

It adjusts the cell’s response to signals.

What does signal integration mean?

Combining multiple signals into one response.

How can signals be integrated?

Through shared signaling proteins or signaling complexes.

What are molecular switches in signaling?

Proteins that switch between active and inactive states.

What are the two types of molecular switches?

• Phosphorylation/dephosphorylation

• GTP binding and hydrolysis

What happens when molecular switches are activated?

They regulate other proteins in the pathway.

What does signal distribution mean?

Sending the signal to different effector proteins.

What types of effector proteins receive signals?

Transcription factors, metabolic enzymes, and cytoskeletal proteins.

Which cell responses are slow?

Responses involving gene expression (like differentiation, division, and growth).

Why are gene expression responses slow?

They require transcription and protein synthesis.

What are examples of cellular responses?

Changes in movement, shape, metabolism, secretion, differentiation, division, growth, and survival.

What is cell differentiation?

The process by which a cell becomes specialized.

What is cell division?

The process by which a cell splits to form new cells.

What is cell growth?

An increase in cell size and/or content.

What does a change in cell metabolism mean?

Altering chemical reactions inside the cell.

What does a change in cell movement involve?

The cell moving or changing direction.

What does a change in cell shape involve?

Structural changes in the cell’s form.

What is secretion in cells?

The release of substances from the cell.

Do all cells respond to all signals?

No, each cell responds to a limited set of signals.

Why do cells respond to different signals?

They have different receptors and signaling pathways.

Do all signal transduction pathways work the same way?

No, they vary in steps and reactions.

Can different cell types respond differently to the same signal?

Yes, they interpret signals differently.

What determines how a cell interprets a signal?

Receptors, intracellular signaling molecules, effector proteins, and other signals.

What does a cell’s response depend on?

The combination of signals it receives.